1. Field of the Invention
The present invention relates to a stowing apparatus of a picture monitor for transportation such as an airplane, a train and a sightseeing bus.
2. Related Art
In a passenger airplane of a airplane, picture monitors (hereinafter referred to "monitors")for explaining passengers about security apparatuses and displaying programmed movies are provided. And, passenger cars and sightseeing buses for party tourists are happened to be provided with similar monitors.
As these monitors, conventionally projectors or CRTs (cathode-ray tube, so called a TV tube) are often employed, but recently liquid crystal panels, which have been increased in definition, have been noticed. In case a liquid crystal panel is used as a monitor, since the size thereof is limited, every group of several passengers is adapted to watch one monitor, further, since the screen of the monitor is small, the monitor is mounted on the ceiling located above the passenger seat. In this case, since the ceiling of the passenger cabin is low, the monitor is adapted to be stowed in a shroud when getting on and off or at the time of emergency to prevent the monitor from being projected to the passenger.
What is requested for this kind of monitor in particular for airplane, when the cabin will lose electric power, the monitor is automatically stowed and is desirably avoided to collide with passengers. Regarding this point, the Federal Aviation Administration (FAA) requires to insure the passengers safety and for monitors to retract totally when electric power to the cabin turned off. It is because, since the monitors protrude downward from the ceiling, the head of the passenger is apt to hit them to cause the passenger to injure himself or damages the monitor.
And, since the appliances in such a passenger cabin will receive vibrations, shocks or acceleration from all directions due to the posture of the airplane or the air stream situation or when taking off, flying and landing, it is a matter of course to clear the safety standard provided by the FAA and on the other hand it is necessary to satisfy the functions to be requested even in the above provided conditions, for instance, in a normal vibration or shock during flight, it is desirable that the monitors in operation do not rotate toward stowing position and stop displaying. Therefore, when the electric power to the monitors is lost, it is necessary to stow the monitors automatically and in addition, desirably, the monitors have better to be stowed when any power more than predetermined value is added.
As a prior art in this field, there is what is disclosed in the Japanese patent laid-open No. Hei 5-97098. In this invention, the following technique is disclosed, that is, when keeping a monitor in operation position (display position), an electric brake is used, and when the passenger cabin loses electric power or the head of a passenger hits the monitor, the monitor will be stowed automatically. And in this invention, when rotating a monitor from the stowing position to the display position and from the display position to the stowing position, the driving power is obtained from an electric motor and the power holding the monitor in the display position is obtained from an electric brake.
In what is disclosed in the above laid-open publication, when the electric power in the passenger cabin is turned off and the monitor is hit with the head of any passenger, the restoring power of sliding clutches and coil spring makes the monitor turned to the stowing position. Therefore, the coil spring functions as a back up (auxiliary) mechanism to the electric motor. And, in this invention, when the monitors are turned from the display position to the stowing position due to the restoring power of the stored energy of the coil spring, the electric motor and the gears connected to the motor are made use of an inertia limiting device for reducing the turning speed of the monitors.
In order to watch the screen of a monitor by any passenger at a seat below the monitor mounted on the ceiling of a passenger airplane, the screen is necessary to face to the passenger. However, in the invention disclosed in the above publication, since a rotation angle of the monitor becomes less than 90.degree. due to its structure, there is a high possibility that the surface of the monitor (front surface of a liquid crystal panel) has to face downward when stowing to cause it to be stained or damaged. On the other hand, when carrying out a maintenance thereof, the monitor is drawn out manually from the stowing position and kept in the displaying position, and the maintenance work is carried out. However, there is a problem in which, the maintenance work in the un-powered state of the monitor has to be carried out so as to keep the monitor not to retract into the stowing position, therefore the maintenance work has not been easy.